I got into nuclear physics only after 1932, after Chadwick discovered the neutron, then you could think of particles in the nucleus.

[Q] I'm asking or... essentially to elicit the statement from you, namely that it was fuzzy and therefore you felt the time was not right to... to do that.

Absolutely, and that people had to talk about electrons in the nucleus and this was obviously impossible because the wave length of an electron was maybe a hundred times the radius of the nucleus, so that didn't make any sense whatever, so you just couldn't do it.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).